The present invention relates to a process for preparing an aqueous dispersion of polymer encapsulated TiO2 particles (TiO2 composites), which are useful in plastics and coatings formulations.
Opacifying pigments such as TiO2 provide opacity (hiding) for coatings and for plastics to conceal the undersurface. It is believed that the efficiency of the pigment is related to the spacing of the pigment particles in the coating or plastic Improvements in spacing can be achieved, for example, by using sulfur acid-functional polymers as dispersants for the pigments in combination with other polymers that at least partially encapsulate the pigment, as disclosed in US Pat. Pub. 2010/0298483. An improvement in the efficiency by which these TiO2 composites can be prepared is disclosed in US Pat. Pub. 2014/0011943. Nevertheless, an ongoing concern with these composites is diminution of freeze-thaw stability. It would therefore be desirable to find a way to prepare a TiO2 composite with improved freeze-thaw stability.